Loading remote images in email messages is turned off by default for your privacy. This helps to keep others from tracking you through the images in their messages to you. When you view an email, you will see this at the top:
However, there are times you want to load images from the people who send you email. You can do that by clicking either the "Allow" button to load only one time or "always allow from" and it will always show you images from that person/sender when they send you messages. It will also add that person to your contacts.
However, to get that to work, you will need to make sure that you have that setting correct in your webmail settings area. Please go to:
Settings > Preferences > Displaying Messages
Then on the right side, there's an option that says "Allow remote resources" and you can choose an option there. Choose "From known senders" if you want to use the button to always allow senders in your contacts to show images and click SAVE at the bottom.
With this option set, you will always see images sent by people in your contacts/address book.
You can, of course, choose "Always" if you don't want to have to mess with it or add all those people to your address book. Just know that there are trackers in most marketing emails, sales, newsletters, etc, and if you load the images, they know you opened the email that they sent you. It's up to you as to how private you want to be there.